Osteotomy is defined as a procedure for surgical division or sectioning of a bone. Displacement osteotomy is the surgical division of a bone and shifting of the divided ends to change the alignment of the bone or to alter weight-bearing stresses. This procedure is typically utilized by orthopedic surgeons to correct for malalignment and malorientation, including uniapical and multiapical deformities of the bone, as well as the treatment for compartmental diseases. The goal of displacement osteotomies is to create congruent matching surfaces to align, stabilize, and maximize contact between the corresponding bone sections. Osteotomies may include a number of different types of bone sectioning procedures that result in two corresponding sections of the bone which are then reoriented until a desired alignment between the bone sections is achieved. In order to improve stability, distribute the load evenly, eliminate abnormal stress, and aid healing, surgeons strive to maximize the match or contact area between two corresponding surfaces when surgically sectioning the bone. Representative types of bone cuts include simple transverse, obliqued cuneiform, stairstep, simple to complex wedges, barrel-vault, and dome shaped cuts. In practice, a surgeon may choose a specific cut configuration in order to achieve a particular reconfiguration of the bone being treated.
Although so called “dome osteotomy” has been known for decades, the term “dome osteotomy” has been used to refer conventionally to semi-cylinder, i.e., half or part (partially) cylindrical, shaped surgical cuts. Specifically, amongst experts within the field, “cylindrical osteotomy” would be a more accurate descriptor for these types of so called “dome”osteotomies, as it is well understood by all to be a cylindrically shaped cut. Although resulting shapes of so called “dome” osteotomy are not domes, the following terms have been used in the scientific literature to refer to osteotomies wherein corresponding bone cuts are shaped like a semi-cylinder: dome, spherical, barrel-vault, focal dome (reversed dome), crescentic, and arcuate. These conventional forms of semi-cylindrically shaped osteotomies are better described as barrel-vault osteotomies, and will be described accordingly herein below. Further, the term “dome osteotomy” has been used in the literature and within the field of corrective osteotomy to describe barrel-vault osteotomy, however, the field of corrective osteotomy has lacked a method and device to accomplish, as described below with respect to the invention herein presented, what will be termed “true dome” or spherical osteotomy.
In barrel-vault osteotomy, a bone is sectioned by oscillating a saw blade around the central axis of the cylinder while cutting the bone. Barrel-vault osteotomy may be used to correct angulation about the central axis of the cylindrical cut and translation along the central axis of the cylindrical cut. The barrel-vault osteotomy provides and allows correction in two-dimensions, which sometimes results in undesirable secondary translation because of imparted limitation of two-dimensional repositioning of the bone portions. In this respect, barrel-vault osteotomy cannot be used to correct axial rotations of the bone without creating gaps and instability between bone segments thereby being a major limitation of so called “barrel-vault” osteotomies. The success of barrel-vault osteotomies relies heavily on meticulous pre-operative planning, and while it may be used to correct radial deformities in the frontal and sagittal planes, one of its major disadvantages is the limited ability to correct axial rotational deformities. Accordingly, it would be desirable to provide a device capable of cutting a bone into corresponding sections that allows for correction in more than two dimensions.
There are a variety of devices and methods available to accomplish these so called “barrel-vault” osteotomies. One method includes drilling a series of holes in the bone along a planned arc. In one example, U.S. Pat. No. 6,190,390 discloses an apparatus and method for the surgical realignment of the knee through proximal tibial osteotomy. The apparatus has an arcuate profile configuration for establishing a series of parallel holes forming the desired semi-cylindrical contour of the barrel-vault cut. In addition to the general disadvantages of “barrel-vault” osteotomies mentioned above, such a method undesirably creates ridges between adjacent sets of drilled parallel holes making alignment more difficult and gaps between bone portions more probable.
According to another example, U.S. Pat. No. 4,955,888 discloses a biradial saw blade with an arcuate body, powered by oscillating motion that is used to create the barrel-vault osteotomy. Such saw blades are typically associated with a saw assembly which operates to displace the blade in a reciprocating motion by oscillating the blade around the drive axis of the saw assembly. The saw blade has a curved cutting edge at the end of the body shaped as a part of a cylinder for making barrel-vault shaped surgical cuts. While the cut resulting from the use of the biradial saw blade provides for a better match of the two surfaces of both bone portions, the heat and friction produced by the saw blade may be detrimental to the bone, specifically for allowing proper healing thereof. Also, other conventional “barrel-vault” saw blades may include a partially cylindrically shaped body having a cutting member on its leading edge.
Conventional blades are limited in providing semi-cylindrical cuts of the bone, which limit the correction in the bone, particularly when correcting deformities that lie in two planes, such as the frontal and sagittal planes. Correction of deformities in two planes requires meticulous preoperative planning in order to determine the central axis about which the cut in the bone is to be made. This is especially crucial if the bone portions are to be properly positioned to correct the deformity. Cutting the bone about a different central axis will only allow, at best, partial correction in the two planes. Further, it is desirable to provide improvement for the correction of malalignment, malorientation and compartmental disease, including other deformities of the bone by osteotomy procedures and tools. Accordingly, it would be desirable to provide an osteotomy tool for cutting bone that increases the adjustability of the bone portions, achieves optimal bone contact, and improves primary stability. It is also desirable to provide an osteotomy tool that is less dependent upon cutting the bone precisely about a determined central axis when attempting to achieve proper correction.
Another disadvantage associated with the use of so-called “barrel-vault”osteotomies is the limited ability to correct axial rotational deformities. Correction of other deformities may also be difficult to make, particularly when a correction of the deformity requires cutting the bone in a less accessible location. This makes it increasingly difficult for a surgeon to provide the corrective cut, as described above, where it is needed. Another disadvantage of barrel-vault osteotomies is the bone portions, after severance, may only be repositioned with respect to one another about two principal dimensions, one of the principal dimensions being an angular displacement or rotation about the central axis, and the other principal dimension being a lateral displacement or position along the central axis. The angular displacement or rotation allows the bone pieces to be rotated with respect to one another about the central axis to the desired correction. The lateral displacement or position allows the bone pieces to be positioned with respect to each other along the central axis to the desired correction. Also, the bone pieces may obtain the desired correction through a small combination of lateral displacements and angular displacements. Lateral displacement of the bone pieces is limited to the extent that the bone portions include sufficient surface contact for proper healing to occur. Angular displacement of the bone pieces provides for better bone-to-bone contact than lateral displacement, however, angular displacement is still limited if the bone portions are to be maintained with sufficient surface contact in order to provide for proper healing. Accordingly, it would be desirable to provide improved osteotomy of a bone to allow for greater surface contact between the repositioned cut pieces. It is further desirable to provide an osteotomy tool for severing a bone to provide correction of the bone pieces in more than two dimensions.
U.S. Pat. No. 5,643,270 discloses a multi-plane curvilinear saw to be used with corresponding guide, and particularly adapted for cutting the bones in a digit, and more specifically for shaping the end of a bone in a digit by ostectomy for fusion with another member of a joint in a digit. Ostectomy refers to surgical removal of a bone or part of a bone. The conventional device is specifically designed to work similarly to a surgical chisel removing cartilage and spongy bone from one side of the joint surface. The saw blade includes a hemispherically shaped body having a flat top and a shank extending from the flat top, and a cutting edge along an exposed edge. This conventional device provides the use of a saw guide in order to ensure accuracy, restrict the movement of the cutting teeth to the path defined by the curved slots, and to avoid slipping of the saw and inadvertent cutting of the surrounding tissue. The saw can be delicately translated, tilted and/or rotated to a limited degree about the end of the bone by the surgeon to make the exact cut until the flat portion of the saw rests flat on the guide. The guide is a necessary component, as without it the saw would slide off the end of the bone. A curved shape occurs on the end of the bone, because the cutting edge with its arc is guided by a saw guide about the arcuate path. Whereas the conventional device is advantageous for general ostectomies for shaping the end of a bone, it is impractical for precise osteotomy of a bone. Such conventional devices undesirably require metal to metal contact between the cutting blade and the guide. Orthopedic surgeons try to avoid contact of the saw blade with other materials (such as metal or plastic) in order to protect their instruments (avoid unnecessary wear and galling), to avoid unnecessary heat production and potential thermal necrosis of the underlying tissue, as well as to avoid material shavings getting into the open wound. Moreover, this conventional device and method are not suitable for true dome osteotomies because, while it may create a curvilinear cut partially into the bone, the device would wedge itself between opposing bone portions during the cutting process due to the shape of the sectioning element or blade. Furthermore, the conventional device may damage the bone by creating too much pressure and heat, caused by friction, during the cutting procedure. Moreover, such conventional devices having a flat top on the upper end of the device restrict full cutting or sectioning of the bone into two portions, particularly when the flat top of the device reaches the parallel surface of the guide with respect to the axis of the bone that prevents complete cutting of the bone.
Accordingly, it would be desirable to provide a device capable of cutting a bone into corresponding sections resulting in a “true dome” or spherical osteotomy.
Accordingly, it is also desirable to provide an osteotomy tool and method for “true dome” or spherical osteotomies that result in two substantially congruent (one concave and one convex) surfaces after cutting a bone.